PIGMENTARY TiO{11

ABSTRACT

Aqueous slurries of pigmentary TiO2 which are rendered resistant to changes in viscosity owing to the presence of Group II metal ions by the addition of monoethanolamine. The monoethanolamine may be applied to the particles before forming the slurry or it may be added to the aqueous slurry after formation.

United States Patent 1191 v Whitehead eta'lf [54] TiQz.

V [75] Inventors: Jack Whitehead; Coulson Lloyd Denton, both ofTeesside, England [73] Assignee: British Titan Limited, Billingham,

' England 1 [22] Filed: Apr. 17, 1973 [211 Appl. 01042351974v [30Foreign Application Priority Data June 27, 1972 Great Britain 2994s 72s2 u.s.-c1.;... 106/300, 106/308 0, 106/308 N 511 1m, 01.... C09c 1/3658 Field at Search 106/308 0, 308 N, 300

[56] References Cited UNITED STATES PATENTS 2,737,460 3/ l 956 Werner106/300 1111 3,808,023 1451 Apr. 30, 1974 3,520,710 7/1970 Kniffin et al106/308 N 3,723,149 3/1973 Francis eta]. 106/308 N 3,412,944 ll/ 1968Wollenberg et al. 106/300 ABSTRACT Aqueous slurries of pigmentary TiOwhich are tendered resistant to changes inviscosity owing to thepresence of Group II metal ions by the addition of monoethanolamine. Themonoethanolamine may be applied to the particles before forming theslurry or it may be added to the aqueous slurry after formation.

12 Claims, No Drawings PIGMENTARY TIO The present invention relates to aprocess for avoiding or reducing increases in the viscosity of aqueousslurries of TiO in the presence of ions of Group ll elements,particularly calcium and, to a lesser extent magnesium ions. Theinvention also includes treated TiO aqueous slurries thereof andproducts such as paper produced by the use of such pigment and/orslurries.

We have found that aqueous slurries containing pigmentary TiO forexample uncoated Ti of the anatase or rutile form, suffer an increase inviscosity in the presence of ions of the elements of Group II of thePerlodic Table. The problem is particularly serious where the ions arecalcium ions and, to a lesser extent magnesium ions. Such an increase inviscosity is most undesirable since it causes problems in the handlingand subsequent use of the aqueous slurry.

The ions may be derived from any source but the main problem arises fromthe use of hard water (containing calcium and/or magnesium ions) and,particularly in paper coating, from'the use of composite pigments of Ti0and calcium carbonate and/or China clay. Even though the solubility ofions of Group II elements, and particularly of calcium and magnesiumions is low, the solubility is normally sufficient to provide theundesired decrease in viscosity.

In the application of TiO to paper, the TiO is normally. uncoated, drymilled anatase Ti0 (although coated anatase TiO- and uncoated and coatedrutile TiO are also used) and it may be applied as an aqueous slurry tothe cellulose or other fibres or the slurry may be applied to thepreformed sheet as a thin film, for example by means of a roller, ablade or by an air knife and it is in this operation that increases inviscosity cause the greatest problems. Even though the viscosity of theinitialaqueous slurry may be satisfactory, increased viscosities maydevelop as the aqueous slurry is recirculated, as it is in acontinuouscoating process for example. The application of increased temperatureand/or increased shear conditions may also contribute to the problem.

Binders, for example modified starches, protein-. aceous materials suchas casein, and synthetic polymers for example of the. latex type, arecommonly added to the aqueous slurries of Ti0 and whereas these mayassist in reducing any increase in viscosity theydo not normally solvethe problem.

It is an object of the present invention to provide TiO pigments for useinaqueous slurries and aqueous slurries thereof wherein an increase inviscosity in the slurry is reduced or prevented.

Accordingly, the present invention comprises pigmentary titanium dioxideparticles coated with monoethanolamine.

The invention also comprises an aqueous slurry of pigmentary titaniumdioxide containing monoethanolamine.

The pigmentary titanium dioxide may be either of the rutile or anatasemodification and it may be uncoated or coated with metal and/ormetalloid oxides prior to the application of the monoethanolamine. It ispre-- ferred, however, that it is uncoated pigmentary anatase titaniumdioxide, for example uncoated dry milled pigmentary anatase titaniumdioxide, since it is with such material that the greatest problems ofincrease of viscosity in aqueous slurries in the presence of Group llions are encountered and, furthermore, such materials are probably themost commonly used TiO pigments in paper manufacture.

The monoethanolamine may be applied to the pigment by any suitablemethod, for example it may be introduced (either undiluted or in asolvent) into an aqueous slurry of the titanium dioxide pigment whichmay then, if desired, be dried and/or milled or it may be introducedinto a fluid energy mill in which the pigment is being milled, forexample by superheated steam, or it may be added at the dry millingstage of the pigment, again either undiluted or in a solvent, forexample in the case of uncoated anatase titanium dioxide. Spray dryingmay be used to dry the pigment after the addition of monoethanolamine,if desired.

After the application of the monoethanolamine the titanium dioxidepigment may, if not already in the form of an aqueous slurry, be formedinto such a slurry for transport and/or for subsequent use, for examplein the pigmentation of paper.

As an alternative to coating the pigmentary titanium dioxide withmonoethanolamine, it is possible that monoethanolamine could be added,normally with vigorous agitation, to a preexisting aqueous slurry of thetitanium dioxide. This method is not, however, preferred since thereaction is slower and because of this a higher proportion ofmonoethanolamine to titanium dioxide is required to obtain a similareffect.

Amounts of monoethanolamine applied as a coating where the pigment issubsequently dried are normally up to 10 percent and preferably in therange 0.1 percent to 2 percent by weight of TiO (on the dry TiOpigment). 7

Where the monoethanolamine is added to a preexisting aqueous slurry ofTiO then quantities of monoethanolamine of up to 10 percent andpreferably up to about 3 percent by weight would normally be used but,as noted previously, larger amounts are required than when themonoethanolamine is applied as a coating.

It has surprisingly been found that monoethanolamine is much moreeffective in reducing or inhibiting an increase in the viscosity ofaqueous slurries of TiO pigment than are either trior di-ethanolamine(hereinafter referred to as TEA and DEA respectively) and, inparticular, the action of monoethanolamine (MBA) is much more prolongedthan is that of the other two ethanolamines mentioned. This is clearlydemonstrated in TABLE 1 of the Examples. The marked tendency of aqueousslurries of Ti0 in the presence of the calcium carbonate and in theabsence of an ethanolamine to changein viscosity is also clearlydemonstrated.

By the term uncoated TiO particles is meantTiO particles of either theanatase or rutile modification free from a coating of any metal ormetalloid oxide such as alumina, silica and/or titania, or any coatingof an organic material, such as an alcohol,- an organic amine or apolyalkylene glycol.

Where coated TiO particles are referred to in this specification theseare pigmentary TiO particles coated with metal and/or metalloid oxidessuch as alumina, silica, titania, zirconia, ceria and/or tin oxides, orv Where metal and/or metalloid oxides are precipitated on to the TiOparticles, amounts in the range of about 0.2% to 10 percent by weight onTiO are normally deposited and preferably amounts in the range 0.5percent to percent for the metal oxides and from 0.5 percent to percentfor silica are used. Such coatings are usually applied by a wet coatingprocess in which the TiO;, particles are formed into an aqueoussuspension to which is added a hydrolysable compound of the metal and/ormetalloid and the pH value of the resulting mixture is adjusted toprecipitate on the particles the hydrous oxide of the metal or metalloidelement. The coated particles are then recovered, dried and milledbefore use.

The following Examples show the results obtained from embodiments of thepresent invention when compared with results obtained by processes notin accordance with the invention.

EXAMPLE 1 A dry milled uncoated anatase titanium dioxide pigment wastaken and divided into four parts. One part was not coated, and theother three parts were coated, respectively with (a) 0.32 percenttriethanolamine, (b) 0.32 percent diethanolamine and (c) 0.32 percentmonoethanolamine. The proportions were by weight on TiO and the coatedprocedure was the same in all cases. All pigments were then formedseparately into 70 percent aqueous slurries and to each slurry was addedsufficient calcium carbonate to provide a 1 percent concentration. Theviscosities of the slurries were measured-at the times shown and theresults are given in Table 1 below:

Pigmentary anatase TiO particles coated with alumina and silica inamounts of 2 percent and 0.7 percent by weight on TiO respectively andwith 0.32 percent monoethanolamine (MEA) were formed into an aqueousslurry containing 60 percent TiO particles and 1 percent calciumcarbonate by weight on TiO At the same time a similar slurry was formedfrom similar pigmentary Ti0 particles (i.e. containing 60 percent of ananatase TiO coated with 2 percent alumina and 0.7 percent silica) butwithout a coating of monoethanolamine.

The slurries were allowed to stand for a prolonged period and theviscosities of the slurries were measured at intervals. The resultsobtaingdare shown in table 2.

The process of Example 2 was repeated using pigmentary rutile TiO coatedonly with 0.32 percent monoethanolamine as a 45 percent aqueous slurryand its viscosity over a period was compared with that of a 45 percentaqueous slurry of uncoated rutile TiO i.e. free from monoethanolamine.

The results obtained are given in Table 3.

TABLE 3 1% CaCO, Hours Untreated +0.32% MEA POiScs EXAMPLE 4 Theprocesses of Examples 2 and 3 were repeated comparing the viscosities ofa 60 percent aqueous slurry of a rutile TiO coated with 4.5 percentalumina, 9.5 percent silica and 0.32 percent monoethanolamine and asimilar slurry of the pigment without the coating of monoethanolamine.

The results obtained are given in Table 4.

TABLE 4 1% CaCO Hours Untreated +0.32% MEA Poiscs 0 4 1.4 1 4 1.4 17 5 l4 20 5 l 4 24 5 1.4 41 5 1.4 48 s -1.4 65 5 1.4 89 S 1.4 161 5 1.4

What is claimed is:

1. An aqueous slurry of pigmentary titanium dioxide particles containingmonoethanolamine.

2. An aqueous slurry of pigmentary titanium dioxide as claimed in claim1 containing not more than 3 percent by weight of monoethanolamine.

3. An aqueous slurry of pigmentary titanium dioxide particles as claimedin claim 1 wherein monoethanolamine is applied to the pigmentarytitanium dioxide particles before slurrying the particles in water.

4. An aqueous slurry of pigmentary titanium dioxide particles as claimedin claim 3 wherein monoethanolamine is applied to uncoated anatasetitanium dioxide particles.

5. An aqueous slurry of pigmentary titanium dioxide particles as claimedin claim 3 wherein monoethanolamine is applied to coated anatase orrutile titanium dioxide.

6. An aqueous slurry of pigmentary titanium dioxide particles as claimedin claim 3 wherein from 0.1 percent to 2 percent of monoethanolamine, byweight on TiO is retained on the particles.

7. An aqueous slurry of pigmentary titanium dioxide particles as claimedin claim 1 wherein the titanium di- 6 oxide particles are coated withfrom 0.2 percent to 10 percent by weight on TiO of a compound comprisingan oxide or a phosphate of a metal or metalloid component said metalbeing selected from the group consisting of alumina, silica, titania,zirconia, ceria and tin.

8. An aqueous slurry of pigmentary titanium dioxide particles as claimedin claim 7 wherein the particles are coated with from 0.5 percent to 5percent of at least one metal oxide and with from 0.2 percent to 10percent of silica.

9. Pigmentary titanium dioxide particles coated with monoethanolamine.

10. Pigmentary titanium dioxide particles as claimed in claim 9 whereinthe monoethanolamine is applied to uncoated anatase titanium dioxideparticles.

11. Pigmentary titanium dioxide particles as claimed in claim 9 whereinthe monoethanolamine is applied to coated anatase or rutile titaniumdioxide particles.

12. Pigmentary titanium dioxide particles as claimed in claim 9 whereinthe particles are coated with from 0.1 to 2 percent of monoethanolamine.

2. An aqueous slurry of pigmentary titanium dioxide as claimed in claim1 containing not more than 3 percent by weight of monoethanolamine. 3.An aqueous slurry of pigmentary titanium dioxide particles as claimed inclaim 1 wherein monoethanolamine is applied to the pigmentary titaniumdioxide particles before slurrying the particles in water.
 4. An aqueousslurry of pigmentary titanium dioxide particles as claimed in claim 3wherein monoethanolamine is applied to uncoated anatase titanium dioxideparticles.
 5. An aqueous slurry of pigmentary titanium dioxide particlesas claimed in claim 3 wherein monoethanolamine is applied to coatedanatase or rutile titanium dioxide.
 6. An aqueous slurry of pigmentarytitanium dioxide particles as claimed in claim 3 wherein from 0.1percent to 2 percent of monoethanolamine, by weight on TiO2, is retainedon the particles.
 7. An aqueous slurry of pigmentary titanium dioxideparticles as claimed in claim 1 wherein the titanium dioxide particlesare coated with from 0.2 percent to 10 percent by weight on TiO2 of acompound comprising an oxide or a phosphate of a metal or metalloidcomponent said metal being selected from the group consisting ofalumina, silica, titania, zirconia, ceria and tin.
 8. An aqueous slurryof pigmentary titanium dioxide particles as claimed in claim 7 whereinthe particles are coated with from 0.5 percent to 5 percent of at leastone metal oxide and with from 0.2 percent to 10 percent of silica. 9.Pigmentary titanium dioxide particles coated with monoethanolamine. 10.Pigmentary titanium dioxide particles as claimed in claim 9 wherein themonoethanolamine is applied to uncoated anatase titanium dioxideparticles.
 11. Pigmentary titanium dioxide particles as claimed in claim9 wherein the monoethanolamine is applied to coated anatase or rutiletitanium dioxide particles.
 12. Pigmentary titanium dioxide particles asclaimed in claim 9 wherein the particles are coated with from 0.1 to 2percent of monoethanolamine.